andrews



Aug. 11, 1959 A. ANDREWS PLUNGER TYPE SOLENOID Filed May 27, 1954 l 3 i H G 2 INVENTOR.

RUFUS A. ANDREWS BY ATTORNEY and/or their fastening means.

United States Patent 2,899,609 PLUNGER TYPE SOLENOID Rufus A. Andrews, Glendale, M0., assignor to Vickers, Incorporated, Detroit, Mich., a corporation of Michigan Application May 27, 1954, Serial No. 432,648 7 Claims. (Cl. 317-191) This invention relates to power transmission and more particularly to plunger type solenoids. In a common form of plunger type solenoid there is provided an energizing coil positioned between the parallel legs of a stator structure, the coil having a plunger-receiving aperture extending axially therethrough and parallel to the stator legs which are connected at one end by an intermediate stator section. It has been known to use numerous types of coil retainers in this type of solenoid, most of them serving the dual purpose of positioning the coil and guiding the plunger. Such coil retainers have been of two general types. One type is an integral extension of a crosspiece fastened to the structure. The second type is non-integral with a crosspiece, but secured against relative movement with respect to the crosspiece by clips, mortise and tenon, slot-mortise and tenon, etc, for example, either the retainer or the crosspiece being engageable on opposite surface by and between two surfaces of the other which is either slotted or re-entrantly bent in clip form to perform the necessary function.

When the desired life of a solenoid is of the order of millions of cycles, solenoids employing coil retainers of the type described are relatively short-lived because of fatigue-caused rupture or distortion of the retainers Retainers integral with cross members rupture at the meeting place of the two sections. In the other type cases involving arrangements wherein either the crosspiece or the retainer is engageable on opposite surfaces by the other as by slotting one to receive the other, or as by forming a clip on one to grip the other, the retainer and/or the crosspiece are subject to distortion and rupture in a relatively short time by the vibration of the solenoid.

In accordance with one embodiment of the invention a solenoid assembly is provided wherein an energizing coil with a plunger receiving aperture is maintained in position between parallel legs of a stator structure by coil retainers which pass through the aperture and are unsecured to any part of the solenoid; the stator structure, coil and the coil retainers being held in interlocked assembled relation by key members in the form of cross elements secured to the structure and extending between the legs and on opposite sides of the plunger.

One aspect of the invention involves the elimination of coil retainer and crosspiece relations wherein one or the other is required to be engageable on opposite surfaces by and between two surfaces of the other as in clip or slot arrangements involving coil retainers found in the prior art. Another and important aspect of the invention is the remarkable ease of assembly, economy of parts and long life in solenoids embodying features of the present invention.

It is therefore an object of the present invention to pro vide a plunger type solenoid assembly with improved coil retaining means.

Another object of the invention is to provide a plunger type solenoid, whose respective components are held together by a novel interlocked assembly arrangement.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is an exploded isometric view of a solenoid embodying features of the present invention.

Fig. 2 is a front elevation of the solenoid shown in Fig. 1.

Fig. 3 is a sectional view of the solenoid shown in Fig. 1 taken on the line 3-3 of Fig. 2; and

Fig. 4 is an isometric view of one of the coil retainers shown in the other figures.

Referring now to the drawings, the solenoid includes a stator structure 12, a plunger type armature 14 and an energizing coil 16.

It should be appreciated that solenoids are generally operable in any position, and that the directional and locating references used in the specification and in the appended claims are arbitrarily keyed to the position of the solenoid as viewed in the drawing without regard to the final mounting direction or position of the solenoid in actual use.

The stator structure 12 includes a generally C-shaped magnetic core 17 with a pair of parallel legs 18-20 connected at corresponding ends by an intermediate section 22. A pair of stubs 24-26 extending inwardly from the legs improve the magnetic circuit relations of the solenoid.

For use with alternating current it is preferred that the core 17 and the armature 14 be laminated. The core 17, as illustrated, is made from a plurality of similar laminations of magnetic material such as silicon steel stacked and riveted together between a pair of side plates 28 and 30 in the usual manner well known in the art. Likewise the plunger armature which is T-shaped is made from a stack of similar laminations riveted together between a pair of side plates 32 and 34.

The coil 16 is wound on a bobbin 36 disposed between the legs 18-20 and provided with an aperture 38 extending through the coil along the winding axis thereof, in which aperture the shank 40 of the plunger 14 is slidably disposed. Hereinafter the winding axis of the coil, which is also the line of travel of the plunger, shall be taken as the axis of the solenoid and all axial references shall be related thereto. Although any other suitable material may be used, nylon has been found to be a preferred material for the coil bobbin because of its ability to successfully endure millions of cycles of slidable engagement with the plunger shank.

The coil bobbin is axially restrained by the stubs 24-26 and the intermediate section 22. A mounting plate or base 42 is secured to the intermediate section 22 by any suitable means, for example, by welding or brazing as indicated at 44. Coincident apertures 46-48 extending axially through the base and the intermediate section 22 provide access to an operating rod 50 which may be contacted and actuated by the shank of the plunger 14 to operate a device linked to the rod 50-, for example a valve.

A pair of partitions 52 and 54 integral with the bobbin and at the upper end thereof, prevent the plunger shank 40 from contacting the ends of the stubs 24-26.

Excessive transverse movement of the coil in any direction would tend to bind the armature. The inner edges of the legs 18-20 are engageable with the bobbin flanges to restrict transverse movement of the coil along a line in the laminar plane and at right angles to the coil axis. Transverse movement of the coil at right angles to the laminar plane is restricted by a pair of coil retainers 56-58 extending through the coil aperture 38 on opposite sides of the plunger.

Inward movement of the lower ends of the retainers is limited by the intermediate section 22 lying between the lower ends of the retainers which extend downward beyond the inner edges 60-62 of the opposite outside surfaces 64-66 of the core section 22. Inward movement of the upper ends of the retainers is limited by a pair of cross elements 68-70 secured to the stator structure by bolts 72 and nuts 74. These cross elements extend between the core legs 18--20 and on opposite sides of the plunger 14. The upper ends of the retainers extend upward, beyond and on the outside of the lower edges of the central sections of the cross elements 68-70. The lower part of each cross element 68-70 is bent outwardly to form an angle or flange section 75 for greater rigidity and to provide greater area for potential contact with the retainers. The flanges also lock the nuts 74.

Each retainer is in the form of an elongated fiat strip (Fig. 4) whose upper end is offset with respect to the main body of the retainer. The offset portion includes a step 76 extending outwardly from the retainer, and an upwardly extending portion 78 having a greater slope than that of the step with respect to the horizontal. The step extends across the entire width of the retainer at the location of the step, and all of the upper end of the retainer is therefore offset from the main body portion of the retainer which extends downward from the step.

The retainers are axially restrained (l) by the cross elements 6870 whose lower edges (flanges 75) are adapted to engage the retainer steps to prevent upward displacement of the retainers, and (2) by the base 42 which functions as an abutment adapted to engage the lower end of the retainers to restrain downward movement of the retainers. The outward extent of the step 76 is substantially greater than the thickness of the retainer in order to present a broad, upwardly facing base for engagement with the flange of the cross element without axial slip which could occur with a step that is too short in the transverse direction at right angles to the laminar planes. In practice excellent results have been achieved with the step having an outward extent of the order of 4 to 6 times as great as the retainer thickness.

The outward extent of the step also provides some axial compensation, if required, to avoid bowing of the retainer within the coil aperture due to axial thrust by the lower edge of the cross element.

A transverse web portion 80 connecting the upper portions of the cross elements 68-70, and forming a unitary structure therewith, extends across the plunger path to function as a bumper or backstop for the plunger. One piece construction including the cross elements and the web portion is a tremendous advantage in assemblying and disassemblying the solenoid, making these operations easy and fast. The integral unit including the cross elements and the web may be referred to as a yoke and is generally designated by the numeral 82.

It will be noted that the cross elements 6370, when secured to the stator structure, function as keys like the last piece in a Chinese puzzle to hold the components together in interlocked relation.

The solenoid is assembled as follows: (1) The coil is fitted between the core legs; (2) the coil retainers are slipped into position with their outer surfaces in contact with the inside surfaces around the coil aperture; (3) the plunger shank is dropped into the coil aperture and between the retainers; and (4) the yoke with the cross elements is placed and fastened in the key position of restricting inward displacement and upward axial displacement of the coil retainers, thus to lock all the components in assembled relation.

It should be noted that the cross elements of the yoke are required to restrain only inward and upward displacement of the coil retainers. Neither the cross elements nor the retainers need to be slotted or bent into clip forms for embracing each other. The coil and the retainers mutually restrain each other transversely, the retainers being restrained from outward movement and the coil from any transverse movement at right angles to the laminar planes by coaction of the outer surfaces of the retainers and the bobbin surfaces 84 defining the coil aperture. Downward movement of the retainers is restrained by any suitable abutment carried by the bob- 4 bin or the intermediate core section 22, such as the base 40. The retainers require no positive fastenings, and are easily slipped in or pulled out by removing only one of the bolts 72 and hinging the yoke 82 back on the other bolt. The only positive fastening employed between any of the components is between the yoke and the stator structure.

Although members 56 and 58 are primarily coil re tainers, they are, in the specific embodiment shown, also operable as plunger guides. The retainers may be made of any suitable material, preferably having the following characteristics: nonmagnetic; wear and abrasion resistance; low coeflicient of dry friction; resilience; and corrosion resistance. Materials such as molded nylon and beryllium copper have these desirable characteristics.

A solenoid made in accordance with the invention herein was successfully operated over 7,000,000 times at the rate of 250 operations per minute.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An electromagnet comprising a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture extending therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, cross member means secured to said structure and extending between said legs and on opposite sides of said plunger, said cross member means and said intermediate section being at opposite ends of said coil, said cross member means having outer surfaces with lower edges, and a pair of coil retainers contacting said coil and extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond and outside of said inner edges and contacting said intermediate section to limit transverse movement of the coil, said section being provided with an abutment means contacting the lower ends of said retainers to prevent axial movement of the coil retainers in only the downward direction, said lower edges of said cross member means contacting the upper ends of said retainers to prevent axial movement of said retainers in only the upward direction and to restrict transverse movement of the retainers in only a direction toward each other.

2. An electromagnet comprising a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture extending therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, a backstop disposed across the path of the plunger and having cross member means secured to and extending between the upper ends of said legs and on opposite sides of said plunger, said cross member means and said intermediate section being at opposite ends of said coil, said cross member means having outwardly directed flanges, and a pair of coil re tainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond said edges and contacting said intermediate section, abutment means independent of said backstop contacting the lower ends of said retainers to prevent axial movement of the coil retainers in only the direction toward said intermediate section, said cross member means contacting the upper ends of said retainers to prevent axial movement of said retainers in only the direction toward said cross member means and to prevent transverse movement of the retainers in only a direction toward each other.

3. An electromagnet comprising a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture extending therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, cross member means secured to said structure and extending between said legs and on opposite sides of said plunger, said cross member means and said intermediate section being at opposite ends of said coil, said cross member means having lower edges, and a pair of coil retainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond and on the outside of said inner edges and contacting said intermediate section to thereby limit transverse movement of the coil, and abutment means independent of said cross member means contacting said lower ends to prevent downward axial movement of the retainers, said retainers having outwardly ofiset portions contacting said cross member means for restricting axial upward movement of said retainers.

4. An electromagnet comprising a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, a yoke secured to said structure and having a transverse web portion across the plunger path and cross elements depending from the web portion and extending between the upper ends of said legs and on opposite sides of said plunger, said cross elements having lower edges, and a pair of coil retainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond said inner edges and contacting the outside of said intermediate section to limit transverse movement of the coil, and abutment means independent of said yoke contacting the lower ends of said retainers to prevent downward axial movement of the coil retainers, each retainer having an outward oflset upper end contacting the lower edge of one of the cross elements to restrict upward axial movement of the retainer.

5. An electromagnet comprising a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, a yoke removably fastened to said legs and having a transverse web portion across the plunger path and cross elements depending from the web portion and extending between the upper ends of said legs and on opposite sides of said plunger, said cross elements having outwardly directed flanges, and a pair of coil retainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond said edges and contacting the outside of said intermediate section to limit inward movement of the lower ends of the retainers, and abutment means independent of said yoke and contacting the lower ends of the coil retainers for restricting downward axial movement of said coil retainers, each retainer having an outward ofifset upper end contacting the flange of one of the cross elements to restrict upward axial movement and inward movement of the retainer, the only positive fastening required to hold the stator, coil, retainers and yoke in interlocked assembled relation being the fastening of the yoke to the legs.

6. In an electromagnet having a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture extending therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, and a backstop to be disposed across the plunger path, said backstop having depending side walls, the combination therewith of means for bolding said components in interlocked assembled relation requiring positive fastening means only between the backstop and the legs, said means comprising flanges integral with said side walls and extending between the upper ends of said legs and on opposite sides of said plunger, said flanges and said intermediate section being at opposite ends of said coil, and a pair of coil retainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond said edges and contacting the outside of said intermediate section to limit transverse movement of the lower ends of the retainers, and abutment means independent of the backstop and flanges and contacting the inner ends of the coil retainers for restricting downward axial movement of the coil retainers, each of said retainers being ofiset outwardly and upwardly at its upper end for engagement with said flanges to restrict upward axial movement of the retainer.

7. In an electromagnet having a stator structure including a pair of parallel legs and an intermediate section joining the lower ends of said legs, said intermediate section having inner edges on opposite sides thereof, an energizing coil disposed between said legs and having a plunger receiving aperture extending therethrough along the winding axis of the coil and substantially parallel to said legs, a plunger having a shank movable along said axis within said aperture, and a backstop to be disposed across the plunger path, said backstop having depending side walls, the combination therewith of means for holding said components in interlocked assembled relation requiring positive fastening means only between the backstop and the legs, said means comprising flanges integral with said side walls and extending between the upper ends of said legs and on opposite sides of said plunger, said flanges and said intermediate section being at opposite ends of said coil, and a pair of coil retainers extending through said aperture on opposite sides of said plunger, the lower ends of said coil retainers extending beyond said edges and contacting the outside of said intermediate section to limit transverse movement of the lower ends of the retainers, and abutment means independent of the backstop and flanges and contacting the lower end of the coil retainers for restricting downward axial movement of the coil retainers, each of said retainers being an elongated flat strip with an offset portion at the upper end including an outward step across the entire width of the retainer at the location of the step, the upper end of the retainer terminating in an upwardly directed part of the offset portion extending from the outer end of the step, said flanges and said offset portions contacting each other to restrict upward axial movement and inward movement of the retainers, the outward extent of the step being substantially greater than the thickness of the retainer.

References Cited in the file of this patent UNITED STATES PATENTS 1,947,291 Ford Feb. 13, 1934 2,459,078 Jeflrey Jan. 11, 1949 2,665,397 Jencks Jan. 5, 1954 

